When I start to drop my pace down (usually anything faster then 5:40 pace or at any pace when I start to get tired) my hip seems to give out. I quickly start to lose control of my leg and compensate somehow in such a manner as to hurt my hip flexor (I think it much be driving me forward rather then my butt/hamstring/hip).
I've done lots of strength work (sideways leg raises and a good amount of balance work that focuses on the hip), but nothing seems to be curing this. In fact, it almost seems that when I am doing the exercises it hurts me.
I also do a lot of stretching of the hip... but this only helps to get me through my easy days.
Basically, nothing I seem to do helps when I go fast.
Any ideas?